The invention concerns a method for sterilizing preforms that are made of a thermoplastic material and are intended for the production of blow-molded containers, in which a sterilizing agent is introduced into the area of the preform and in which the preforms are heated before they are blow molded.
In addition, the invention concerns a device for blow molding at least partly sterile containers by deforming a preform, said device having a delivery device for applying a sterilizing agent to at least part of the preform.
Finally, the invention concerns a device for sterilizing preforms that are made of a thermoplastic material and are intended for the production of blow-molded containers. The invention also comprises a device for producing at least partly sterile containers made of a thermoplastic material.
The invention also concerns a device for blow molding containers, which has at least one blowing station mounted on a support structure for blow molding thermoplastic preforms into containers.
Sterile blow-molded containers are typically produced by sterilizing the containers with hydrogen peroxide or other chemicals after they have been blow molded and before they are filled with a product. It is also well known that the preforms used as the starting product in the blow molding of the containers can be sterilized, especially the area of the inner surface of the preforms.
In container molding by the action of blowing pressure, preforms made of a thermoplastic material, for example, preforms made of PET (polyethylene terephthalate), are fed to different processing stations within a blow-molding machine. A blow-molding machine of this type typically has a heating system and a blowing system, in which the preform, which has first been brought to a desired temperature, is expanded by biaxial orientation to form a container. The expansion is effected by means of compressed air, which is fed into the preform to be expanded. DE-OS 43 40 291 explains the process-engineering sequence in this type of expansion of the preform.
The basic structure of a blowing station for container molding is described in DE-OS 42 12 583. Possible means of bringing the preforms to the desired temperature are explained in DE-OS 23 52 926.
Various handling devices can be used to convey the preforms and the blow-molded containers within the blow-molding device. The use of transport mandrels, onto which the preforms are slipped, has proven especially effective. However, the preforms can also be handled with other supporting devices. Other available designs are grippers for handling the preforms and expanding mandrels, which can be inserted in the mouth region of the preform to support the preform.
The handling of containers with the use of transfer wheels is described, for example, in DE-OS 199 06 438 with the transfer wheel arranged between a blowing wheel and a delivery line.
The above-explained handling of the preforms occurs, for one thing, in so-called two-step processes, in which the preforms are first produced by injection molding and temporarily stored and then later conditioned with respect to their temperature and blown into containers. For another, the preforms can be handled in so-called one-step processes, in which the preforms are first produced by injection molding and allowed to solidify sufficiently and are then immediately suitably conditioned with respect to their temperature and then blow molded.
With respect to the blowing stations that are used, various embodiments are known. In the case of blowing stations that are arranged on rotating transport wheels, book-like opening of the mold supports is often encountered. However, it is also possible to use mold supports that can be moved relative to each other or that are supported in a different way. In stationary blowing stations, which are suitable especially for accommodating several cavities for container molding, plates arranged parallel to one another are typically used as mold supports.
With respect to the sterilization of preforms, various prior-art methods and devices already exist, but they all have process-specific disadvantages that stand in the way of reliable sterilization of the preforms when high throughput rates are required at the same time.
EP 1 086 019 A, for example, describes the sterilization of hot preforms with a hot gaseous sterilizing agent. A succession of separate processing stations is used, namely, a first heating module, a sterilization module, and a second heating module. Disadvantages of this system are the temperature behavior of the preform during the sterilization process and the uncontrolled escape of the sterilizing agent from the preform within the heating stage.
EP 1 896 245 A describes a method in which a gaseous sterilizing agent is introduced into a cold preform and condensed therein before the preform is heated. A problem with this method is the difficulty of ensuring complete formation of condensate on the entire inner surface of the preform, since the hot sterilizing agent flowing into the preform raises the temperature of its inside wall. In addition, this method also allows uncontrolled escape of the sterilizing agent from the preform within the heating stage after it vaporizes in the heating zone.
EP 2 138 298 A describes a device in which, as a precautionary measure, sterilizing devices are arranged both upstream and downstream of the blowing module. This results in very high mechanical engineering expense.
WO 2010/020530 A1 describes the arrangement of a sterilization device between a heating device and the blowing module. In this method, the amount of sterilizing agent introduced into the area of the blowing module is difficult to predict. In addition, the amount of sterilizing agent released into the environment cannot be controlled, so that environmental contamination cannot be ruled out.